Air tool

ABSTRACT

An air tool which incorporates a plurality of pistons connected to a common elongated rod, each piston being received within one of a series of aligned cylinders and communicated with a source of pressurized air whereby the pressurized air will act equally upon the multiple pistons and provide for a substantial amplification of the operating force derived from the pressurized air. The two flow paths provided comprise one extending longitudinally through the piston rod itself and the other surrounding the cylinders within a cylinder enclosing housing. Also, with selected ones of the piston receiving cylinders, one way check valves can be provided for enabling the creation of a vacuum upon a forward stroke so as to assist in amplifying the force of the return stroke.

United States Patent Inventor Charles D. Bruyn Vails Gate, N.Y. Appl. No. 773,886 Filed Nov. 6, 1968 Patented Jan. 12, 1971 Assignee James Henry Bruyn Newburgh, N.Y. a part interest AIR TOOL 21 Claims, 11 Drawing Figs.

US. Cl 91/411, 91/413, 92/1 1 1,92/151 Int. Cl ..'..Fl5b 11/06, I

, F0lb 7/00 Field of Search 91/413, 41 1A; 92/151, 146, 128; 60/57, 62,60

References Cited UNIT ED STATES PATENTS 825,866 7/1906 Rogers 92/151 ",3 a g nm Primary Examiner-Edgar W. Geoghegan Attorneys-Clarence A. O'Brien and Harvey B. Jacobson ABSTRACT: An air tool which incorporates a plurality of pistons connected to a common elongated rod, each piston being received within one of a series of aligned cylinders and communicated with a source of pressurized air whereby the pressurized air will act equally upon the multiple pistons and provide for a substantial amplification of the operating force derived from the pressurized air. The two flow paths provided comprise one extending longitudinally through the piston rod itself and the other surrounding the cylinders within a cylinder enclosing housing. Also, with selected ones of the piston receiving cylinders, one way check valves can be. provided for enabling the creation of a vacuum upon a forward stroke so as to assist in amplifying the force of the return stroke.

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PATENTEUJANIZIBYI 4 3,654,086

I SHEET 1 UF 5 Charles 0. Bruyn IN L/ISNI'UK.

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AIR TOOL I The instant invention is generally concerned with a pneumatic tool wherein multiple pistons are mounted on a common piston rod and operative within multiple cylinders, each communicated with a common source of pressurized air for an amplification of the resultant force.

It is a primary object of the instant invention to provide for a unique arrangement of elements which enable the achievement of a substantial force amplification in a small hand manipulatable tool, the operative elements being located within a compact body devoid of encumbering projections or the like.

Another significant object of the instant invention resides in the provision of a power unit which is adaptable 'to a wide variety of tools, including rivet pullers, staplers, nailers, and other types of driving or pulling implements.

Furthermore, an important object of the instant invention resides in the provision of a tool which is, while'highly unique, structurally simple and operationally dependable.

Basically, the tool of the instant invention is sectional in construction, including a plurality of cylinders longitudinally mounted within a slightly enlarged body whereby air passage means is defined within the body about the cylinders. Each cylinder receivesa piston therein which, through a sectional piston rod, is aligned and cooperates with the remaining pistons in-providing for an amplification of the force derived from the air pressure supplied. An appropriate control valve system is utilizedfor directing the intake of air so as to selectively advance and retract the pistons, and an appropriate workhead is mounted on'the forward end of the rod and operates on the workpiece in response to the extension and retraction of the piston rod.

These together with other objects and advantages which will become subsequentlyapparent reside in the details of-construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout, and in which:

FIG. 1 is a perspective view of a rivet pulling tool incorporating the features of the instant invention;

FIG. 2 is a partial perspective view, with portions broken away and exploded, of the tool body and handle;

FIG. 3 is an enlarged transverse cross-sectional view taken substantially on a plane passing along line 3-3 of FIG. 1;

FIG. 4 illustrates the work to be performed by the particular tool illustrated;

FIG. 5 is an exploded perspective view of the force amplifying elements of the tool;

FIG. 6 is a rear elevational view of a modified tool;

FIG. 7 is a cross-sectional view of the modified tool taken substantially on a plane passing along line 7-7 in FIG. 6;

FIG. 8 is an enlarged cross-sectional view taken substantially on a plane passing along line 8-8 in FIG. 7;

FIG. 9 is an enlarged cross-sectional detail of several of the components of the modified tool;

FIG. 10 is an exploded perspective view of the operating elements of the modified tool; and

FIG. 11 is a further exploded perspective view of several of the components.

Referring now more specifically to the drawings, reference numeral is used to generally designate a tool incorporating the advantages of the instant invention. The particular tool illustrated is a rivet puller which operates in the manner suggested in FIGS; land 4, this basically involving an extension of the chuck 22 into gripping engagement with a naillike rivet expander 24 which, upon a retraction of the chuck 22, is drawn rearwardly so as to expand the rivet 26 and subsequently broken, leaving the rivet expanding head thereof locked within the rivet. It will of course be appreciated that the operative components of the tool, as shall be explained in detail subsequently, are equally adapted to a variety of other types of'handtools, however, the utilization of the features of this invention in a rivet pulling tool is considered particularly advantageous in view of the extreme force needed to pull the rivets and the manner in which the resultant tool can be of a compact easily handled size.

The tool 20, regardless of the particular workhead to be associated therewith, includes an elongated hollow cylindrical body 28 including open internally threaded forward and rear end portions 30 and 32. In addition, the cylindrical body 28 includes, inwardly offset from the forward end portion 30 thereof, an annular inwardly offset smooth piston receiving portion or cylinder 34presenting forwardly and rearwardly directed annular shoulders 36 and 38.

A cylinder head 40, including an annular sealing ring 42 thereabout, is seated within the forward end of the integral cylinder 34, this head 40 including an annular flange 44 thereabout which seats on the forward cylinder forming shoulder 36. An externally threaded forward end cap 46 is threaded within the internally threaded forward end 30 of the body 28. The cap 46, hollow so as to define a forward cylinder 48, extends a sufficient distance into the forward end portion of the body 28 so as to clampingly engage the cylinder head 40 into position against the annular shoulder 36. Actually, the external threads on the cap 46 are provided on an intermediate portion thereof, terminating short of the inner portion of the cap so as to provide for an annular air space 50 about the inner end portion of the cap 46 between the cap 46 and the cylindrical body 28. In addition, the threaded'portion of the cap 46 terminates short of the outer end portion of the cap which is slightly enlarged relative to the body received threaded portion so as to seat against and provide for a smooth continuation of the body. In order to communicate the interior of the cylinder 48 with the annular space 50, suitable airflow permitting notches 52 are provided at spaced points through the inner edge portion of the cap 46.

A hollow rear end cap 54 includes an externally threaded forward portion 56 which is threaded within the internally threaded rear end portion 32 of the body 28 and defines a piston receiving cylinder 58. A cylinder head 60 is sealingly received within the internal forward end portion of the cylinder 58, the cylinder head 60 including an annular flange 62 thereabout which bears against the extreme annular forward end of the cap 54 so as to properly orientate the head 60.

A series of intermediate cylinders 64 are defined between the integrally formed cylinder 34 and the rear cap cylinder 58 by a series of cylindrical walls 66 of a slightly lesser diameter than the interior of the cylindrical body 28 so as to define an air space 68 about the cylinders 64 within the body 28 itself. The intermediate cylinders 64, two appearing in the illustrated embodiment of FIG. 3, are separated from each other by an intermediate cylinder head 70 which is sealingly received within the rear cylinder 64 and positioned therein by an appropriate annular flange 72 seating against the annular forward edge of the associated cylinder wall 66. The rear edge of the rearmost one of the cylinder walls 66 seats against the positioning flange 62 associated with the cap formed cylinder 58. The forwardmost ones of the cylinders 64 in turn sealingly receives a cylinder head 74 within the forward end portion thereof, the cylinder head 74 including an annular enlarged flange thereon which seats both against the rear edge 38 of the integral cylinder 34 and the annular forward edge of the forwardmost cylinder wall 66. It should of course be appreciated that the cylindrical body 28 is of a length whereby upon a mounting of the end caps 46 and 54 the aforedescribed cylinder heads and internal cylinders shall assume a reasonably snug relationship relative to each other as illustrated in FIG. 3.

Both cylinders 64 as well as the cylinder 34 are to be communicated with the encircling air space 68. As such, the rear end portions of both cylinder forming walls 66 are provided A sliding piston 80 is slidably provided in each of the cylin ders, such pistons 80 being mounted on a common piston rod 82 which extends longitudinally through the cylinder heads and forward cap 46, being appropriately sealed relative thereto by suitable O-ring seals.

The piston rod 82 is essentially formed by a plurality of hollow communicating releasably interconnected piston rod sections 84, including a forwardmost section 84' and a rearmost section 84". Each of these piston rod sections includes a reduced diameter rear portion which defines an annular shoulder against which one of the pistons 80 seats. The reduced diameter rear portion associated with the rearmost piston rod section 84" is of a length corresponding approximately to the thickness of the rearmost piston 80 and is internally threaded for the reception of a mounting bolt 86 which mounts the rearmost piston 80 thereon. The reduced diameter rearmost portions of the remainder of the sections are externally threaded and threadedly received within the internally threaded forwardmost portions of the rod sections immediately rearward thereof. Each of the rod sections 84 and 84" also includes an outwardly directed annular flange 88 about the forward end thereof, such flanges 88 defining seats for the pistons 80 located in the chambers 48, 34 and 64. These pistons 80 are in turn firmly clamped against the rod section flanges 88 by the shoulders defined by the reduced rear end portions of the piston rod sections immediately forward thereof. It is believed that this arrangement will be readily apparent from a consideration of FIGv 3. With the piston rod 82 so assembled, it will be noted that a continuous air passage is formed therethrough from the rear mounting bolt 86 through the rear portion of the forward rod section 84 to a point corresponding approximately to the forward wall of the forward most cylinder 48. This internal air passage, hereinafter designated by reference numeral 90, is in turn communicated with each of the cylinders by means of lateral air passages or openings 92, at least one being provided immediately forward of each piston 80 and so located as to remain in communication with the corresponding chamber at the forwardmost limit of the travel of the corresponding piston 80.

A control handle 94 is provided, normally integrally, on the cylindrical body 28 and depends therefrom. This handle 94 includes conventional means (not illustrated) for engagement with both inlet and outlet air hoses for the supply and exhausting of air under pressure. Such air lines will, when connected, communicate with an air inlet passage 96 and an air exhaust passage 98. A pair of cooperating valve units 100 and 102 are communicated between the air passages 96 and 98, and air passages 104 and 106. The air passage 104 communicates with the air space 68 surrounding the cylinders 64, and the air passage 106 extends into the cylinder 34 forward of the piston 80 therein for communication with the central air passage 90 through the piston rod 82. In order to provide for an adequate flow of air between the piston rod passage 90 and the airflow passage 106, a plurality of the lateral air openings 92 can be provided circumferentially about the piston rod 82 within the cylinder 34 forward of the associated piston 80. Further, it will of course be appreciated that the air passage 106 is communicated with the cylinder 34 at a point forward of the forwardmost position assumed by the piston 80 in this particular cylinder. A pivotally mounted trigger 108 is provided between and in engagement with the two valve units 100 and 102 for a control thereof in selectively directing the pressure to either the air passage 104 or the air passage 106.

The valve unit 100 consists basically of a pair of valves 110 and 112 selectively engageable with a pair of opposed valve seats 114 and 116. A valve spacing pin 118 extends through a reduced passage connecting the seats 114 and 116, the pin 118 orientating the valves 110 and 112 relative to each other so as to provide for an unseating of one of the valves upon a seating of the other valve. A biasing spring 120 provided inward of the valve 112 normally biases the valve 112 against its seat along with a corresponding movement of the valve 110 away from its seat. A sliding plunger 122 projects forwardly from engagement with the valve 110 into engagement with the lower portion of the trigger 108 which is in turn, in its at rest position, biased forwardly by a coiled biasing spring 124 encircling the plunger 122.

The valve unit 102 is of a construction generally similar to that of the valve unit 100 in that it incorporates a pair of pin spaced valves 126 and 128 orientated relative to each other in a manner whereby upon the seating of one of the valves the other valve unseats, this seating occurring to the opposite sides of a reduced passage through which the spacing pin 130 projects. A biasing spring 132 is located inward of an in engagement with the inner valve 128, this spring, in the absence of an external force, being sufficient to bias the valve 128 into engagement with its seat and correspondingly bias the valve 126 away from its seat. However, the main biasing spring 124 associated with the valve unit 100 is productive of a biasing force sufficient so as to, through a pivoting of the trigger 108 which engages against a plunger 134 in the valve unit 102, compress the spring 132, unseating the valve 128 and seating the valve 126. Thus the at rest position of the control apparatus is as illustrated in H6. 3. ln this position, air entering through the air inlet passage 96 will travel through a chamber behind the seated valve 112, through an air passage 136 into the chamber receiving the unseated valve 128, and from there through a passage 138 communicated with the air passage 104 which in turn directs the incoming air to the cylinder surrounding space 68. The air in the space 68 in turn passes into the three intermediate cylinders 64 and 34, such being the only cylinders communicated with the space 68. This introduction of pressurized air into the three cylinders forces the pistons therein, as well as the attached piston rod. forwardly so as to extend the workhead 22. This forward movement of the piston rod 82 of course also effects a forward movement of the two pistons 80 in the two end cylinders 48 and 58, notwithstanding the lack of communication of the cylinders with the incoming air. This forward movement of the two end pistons results in the creation of a vacuum in the rear chambers of the two end cylinders 48 and 58 which is considered highly significant in substantially amplifying the return or working stroke of the piston 82, acting somewhat in the manner of a return spring, while at the same time eliminating such a spring and the defects and structural limitations incident to the use of such a spring. During this forward stroke, it will be appreciated that the exhausting air will move through the hollow passage within the piston rod itself, exhausting through the passage 106 into a diagonal passage 140 which bypasses the valve unit 102 and communicates with the valve unit in the reduced passage which receives the valve spacing pin 118. The exhausting air then moves by the unseated valve and through the exhaust air line 98.

When a return stroke of the piston rod 82 is desired, the trigger 108 is pulled, seating the valves 110 and 128 and unseating the valves 116 and 126. The air intake passage 96 is then communicated with the air lines and 106 for an introduction of the air into the hollow passage 90 of the piston rod 82 for discharge into all of the cylinders forward of the pistons 80 therein. At the same time, the air exhaust line 98 is communicated with the air passage 104 and the cylinder surrounding air space 68 for an exhausting of the air in the three intermediate cylinders. Upon a rearward or retracting movement of the pistons 80 in the front and rear cylinders 48 and 58, any air trapped therein will be allowed to escape through appropriate one-way check valves 142 and 144, the valve 142 communicating with the small air space 50 surrounding the inner end of the cylinder 48 and communicated therewith by the notches 52, and the check valve 144 communicated directly with the interior of the cylinder 58 through the end cap 54 itself. The presence of air to the rear of the front and rear pistons 80 associated with the front and rear cylinders 48 and 58, will normally occur during periods of nonuse, notwithstanding the practically sealed nature of these chambers which is utilized to develop the return stroke amplifying vacuums. As such, in most instances, as an initial step to using the tool after a period of nonuse, prior to an engagement with the workpiece, the trigger will be pulled so as to retract the rod 82 and pistons, expelling the air from the forward and rear vacuum chambers. Thus, upon a release of the trigger and a forwardmovement of the pistons, the desired vacuum will be developed in conjunction with a gripping of the workpiece by the appropriate workhead or chuck 22, after which the trigger 108 can again be pulled so as to effect the powered return stroke amplified by the two vacuum chambers. Incidently, one additional advantage residing in the formation of the cylinders 64 by cylindrical walls or sleeves 66 is to make these cylinders in fact floating cylinders capable of compensating for any slight misalignment of the pistons or rod sections without affecting the operation of the tool.

Insofar as the structure provided on the forward end of the tool of FIG. 3 is concerned, such consists essentially of a chuck cover 146 mounting a hollow chuck opening abutment 148 for engagement by the forwardly moving chuck so as to spread the jaws thereof for gripping reception to the shank of a pin 24 or the like which can be inserted through the abutment forming member 148.

Attention is now particularly directed to FIGS. 611 wherein a modified tool 150 is illustrated. The tool 150, similar to the tool 20, also uses a multiple cylinder and piston arrangement'operative in conjunction with a common piston rod 152 extending longitudinally therethrough.

Each of thecylinders 154' is defined by a cylindrical wall 156 having an integral cylinder head 158 on the forward end thereof. The cylindrical wall 156 is inwardly offset peripherally about the cylinder head 158, as indicated by reference numeral 160, and is internally enlarged at the other end thereof, as indicated by referencenumeral 162. An internal abutment shoulder 164 is defined by the internally enlarged end portion 162 with this abutment shoulder seating against the slightly inwardly offset cylinder head 158 of a cylinder 154 immediately to the rear thereof, the length of the internal offset portion 162 being slightly less than the external offset portion 160 so as to provide in effect an annular groove 166 about the joined cylinders which is in turn directly communicated with the adjoining cylinder 154 by means of radial air passages 168 provided through the inwardly offset end portion 160 immediately behind the cylinder head 158. It will also be noted that an appropriateO-ring seal 170 is provided about the cylinder head 158 so as to seal the open end portion 162 of the cylinder 154 which engages thereabout. With reference to FIG. 7, it will be appreciated that the stacked cylinders 154 are positioned within a slightly enlarged hollow bor 172 pro vided in the body 174 of the tool 150. The forwardmost cylinder has a modified head 176 thereon which is sealed against the closed forward end 178 of the bore 172 by means of an appropriate O-ring 180, while the last or rearmost cylinder has a modified flat rear end portion 182 appropriately sealed against a body end cap 184 releasably bolted on the body subsequent to the introduction of the various operating components.

The piston rod 152 includes an elongated hollow shaft 186 having an enlarged head 188 on the rear end thereof slidably received centrally through the end cap 184 and sealed relative thereto by. an appropriate O-ring seal 190. The shaft 186 is surrounded by a plurality of slightly enlarged tubular piston rod sections 192, each of which has a cylinder receivedpiston 194 integral with the rear end thereof. The rearmost piston 194 seats against anannular shoulder defined by the enlarged head 188 on the shaft 186 with each of the subsequent pistons 194 seating on an annular recessed shoulder 196 provided on the leading end of the piston rod section 192 immediately therebehind. The pistons 194, as previously indicated, are of course arranged one in each cylinder 154.

The forwardmost piston rod section 198 is modified as compared to the remainder of the sections 192, the section 198 beingsubstantially longer and extending through the leading cylinder head 176, the forward end of the body 174, and an extemallv threaded mounting boss 200 on the body. The leading end of the rod section 198 is provided with an appropriate internally threaded bore 202 for the mounting of a chuck or working head 204, while the trailing end of the rod section 198 is provided with an enlarged internally threaded bore 206 for threaded engagement on the externally threaded forward end of the shaft 186 in a manner so as to cla'r'npingly mount all of the rod sections on the shaft 186. The individual piston rod sections 192 are of course slidably received through the cylinder heads 158 and appropriately sealed thereto by O-ring seals 208.

Referring particularly to FIG. 8, it will be noted that the bore 172 through the tool body 174 is eccentric-ally located. providing for a greater thickness of the body beneath the bore. An elongated air passage 210 is provided longitudinally through this thickened portion, commencing at the rear of the body 174 and terminating in a laterally directed forward end portion 212 which communicates with the bore 172 immediately adjacent and slightly forward of the forwardmost cylinder head 176. In addition, in alignment with each annular groove 166, defined between the adjacent cylinders 154. the bore is provided with arcuate grooves 214 which are of a depth so as to intersect the air passage 210 for a communicationof the air passage 210 with the bore 172 at these points. By the same token, at these particular points, it will be appreciated that communication will also be had with the interiors of the cylinders 154 immediately forward of the pistons 194 by means of the air passing openings 168, the forward cylinder head 176 having similar air passing openings 216 therethrough. Further, the bore 172 is slightly larger than the annular cylinder walls 156 so as to actually provide for a flow of air completely thereabout whereby the interior of the bore 172 is used as an air passage, in addition .to providing for the accommodation of anyslight misalignment without affecting the operation of the unit. The initial manifold type air passage 210 is itself communicated with an air passage 218 which, through an appropriate valve structure such as illustrated in FIG. 3, will selectively be an air intake or exhaust.

A second air passage or air line 220 extends from the valve control unit into communication with an annular air space 222 provided about the forwardmost piston rod section 198, this air space being directly communicated with the hollow interior 224 of the centrally located shaft 186. This hollow interior is closedat the rear end thereof by an appropriate plug 226 and is provided, at suitable points along the length thereof, with lateral air passing openings 228 which provide for a discharge of air into the slightly enlarged rod sections 192. Each of the rod sections, noting FIG. 9 in particular, is itself provided with air passages 230 extending generally laterally therefrom through the associated piston 194 into communication with the corresponding cylinder 154 to the rear of the piston 194. Thus communication is made with each cylinder 154 to the opposite sides of the piston 194 therein, providing for, through the control valve unit, a selective power driving of the piston rod in opposed directions withthe multiple piston and cylinder arrangement providing for a substantial force amplification, and with the structural arrangement of components, including the air passage forming bore, providing for the incorporation of the force amplification arrangement in a compact handtool.

From the foregoing, it will be appreciated that a unique handtool has been defined, such being in the nature of an air tool whereby a multiple amplification of the force is achieved through the utilization of a series of pistons and cylinders and a common piston rod. The tool itself is, through the unique internal construction thereof, highly compact and capable of being constructed in a size corresponding to that of any conventional power handtool, such as an electric drill or the like, notwithstanding the substantial force amplification achieved. As an example of the compactness of the tool, the overall length of the tool in FIG. 1 need not be over 10 or ll inches long to achieve more than ample force for the purpose of pulling rivets, normally an extremely difficult task. Further, at least in one embodiment of the invention, it is contemplated that the force on the actual working stroke be even further amplified through the provision for a vacuum acting in the nature of a return spring.

The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.

lclaim:

l. A force amplifying tool comprising a series of longitudinally aligned cylinders, a piston operatively disposed in each cylinder, an elongated piston rod extending slidably through said cylinders and engaged with said pistons, one end of said rod being adapted to mount a workhead, each piston defining forward and rear chambers in the corresponding cylinder, first fluid passage means communicating with all of the forward chambers, second fluid passage means communicating with at least a major number of the rear chambers, and an elongated tubular body enclosing said cylinders and fluid passage means, one of said fluid passage means being defined longitudinally through said piston rod, said rod having laterally directed holes therein communicating the interior fluid passage means with the corresponding chambers, the other of said fluid passage means being defined about said cylinders between the cylinders and the tubular body, and fluid passing holes communicating said other fluid passage means with the corresponding chambers, said elongated piston rod being formed of a plurality of releasably interconnected hollow rod sections, at least the majority of said pistons being mounted between adjacent rod sections, each cylinder being defined by an independent cylindrical wall releasably engageable with the cylindrical walls of the adjoining cylinders so as to define the series of longitudinally aligned cylinders, said tubular body including at least one removable end cap thereon for the introduction of the sectionally constructed rod and cylinders.

2. The tool of claim 1 wherein each of said rear chambers not communicated with the second fluid passage means is substantially airtight upon forward movement of the piston therein whereby a vacuumlike condition is developed which provides an inherent retracting force on the piston and hence the piston rod.

3. The tool of claim 2 including a one-way check valve in each of said rear chambers not communicated with the second fluid passage means providing for an exhausting of air in the corresponding rear chamber upon a rearward movement of the corresponding piston.

4. The tool of claim 3 wherein one of said cylinders is integrally formed with and interiorly within said tubular body.

5. The tool of claim 4 wherein the fluid passage means through the piston rod comprises the first fluid passage means, and the fluid passage means about the cylinders comprises the second fluid passage means.

6. A force amplifying tool comprising a series of longitudinally aligned cylinders, a piston operatively disposed in each cylinder, an elongated piston rod extending slidably through said cylinders and engaged with said pistons, one end of said rod being adapted to mount a workhead, each piston defining forward and rear chambers in the corresponding cylinder, first fluid passage means communicating with all of the forward chambers, second fluid passage means communicating with at least a major number of the rear chambers, and an elongated tubular body enclosing said cylinders and fluid passage means, said elongated piston rod being formed of a plurality of releasably interconnected hollow rod sections, at least the majority of said pistons being mounted between adjacent rod sections, each cylinder being defined by an independent cylindrical wall releasably engageable with the cylindrical walls of the adjoining cylinders so as to define the series of longitudinally aligned cylinders, said tubular body including at least one removable end cap thereon for the introduction of the sectionally constructed rod and cylinders.

7. A force amplifying tool comprising a series of longitudinally aligned cylinders, a piston operatively disposed in each cylinder, an elongated piston rod extending slidably through said cylinders and engaged with said pistons, one end of said rod being adapted to mount a workhead, each piston defining forward and rear chambers in the corresponding cylinder, first fluid passage means communicating with all of the forward chambers, second fluid passage means communicating with at least a major number of the rear chambers, and an elongated tubular body enclosing said cylinders and fluid passage means, each of said rear chambers not communicated with the second fluid passage means being substantially airtight upon forward movement of the piston therein whereby a vacuumlike condition is developed which provides an inherent retracting force on the piston and hence the piston rod.

8. The tool of claim 1 wherein the fluid passage means through the piston rod comprises the second fluid passage means, and the fluid passage means about the cylinders comprises the first fluid passage means.

9. The tool of claim 8 wherein each of said pistons is integrally formed with one of said piston rod sections.

10. The tool of claim 9 including a one-piece elongated hollow shaft extending through the piston rod sections, said shaft defining an internal airflow passage and having lateral openings therethrough communicating with the interior of said piston rod sections, and means on the opposite ends of said shaft for engagement with the endmost piston rod sections in a section clamping manner.

11. The tool of claim 10 including an elongated air passage defined through said body parallel to the cylinder receiving interior thereof and communicated with the cylinder receiving interior thereof via lateral openings.

12. A force amplifying tool comprising a series of longitudinally aligned cylinders, a piston operatively disposed in each cylinder, an elongated piston rod extending through said cylinders and engaged with said pistons, each piston defining a forward and a rearward chamber in the corresponding cylinder, first airflow means communicated with all of the forward chambers, second airflow means communicated with the rear chambers of a major number 05 said cylinders, check valve means associated with the rear chambers not communicated with the second airflow means for precluding an introduction of air into said chambers upon a forward movement of the associated pistons whereby a vacuumlike condition is developed therein, and allowing an exhaust of these rear chambers upon a rearward movement of the pistons therein, the pistons in the cylinders having the noncommunicating rear chambers being fixed to the piston rod for forward movement therewith induced by the introduction of pressure through the airflow means communicating with the rear chambers of those cylinders wherein the rear chambers communicate with the second airflow means.

13. The tool of claim 12 wherein said first airflow means is defined longitudinally through said piston rod.

14. The tool of claim 12 wherein said second airflow means is defined substantially circumferentially about the cylinders having the communicated rear chambers.

15. The tool of claim 12 including a pair of cooperating valve units for controlling the flow of air through the first and second airflow means, each valve unit including a pair of spaced valves and spaced valve seats orientated relative to the valves so as to provide for a seating of only one valve at a time, and spring means biasing each valve unit to a predetermined position.

16. The tool of claim 7 including a one-way check valve in each of said rear chambers not communicated with the second fluid passage means providing for an exhausting of air in the corresponding rear chamber upon a rearward movement of the corresponding piston.

17. The tool of claim 7 wherein one of said cylinders is integrally formed with and interiorly within said tubular body, the remainder of said cylinders being independent of said tubular body and positioned generally concentrically therewith.

, means being substantially airtight upon forward movement of the piston therein whereby a -va'cuumlike condition is developed which provides an inherentretracting force on the piston and hence the piston rod.

19, The tool of claim 18 including a one-way check valve in a each of said rear chambers not communicated with the second fluid passage means providing for an exhausting of air inthe corresponding rear chamber upon a rearward movement of the corresponding piston.

20. A force amplifying tool comprising a series of longitudinally aligned cylinders, a piston operatively disposed in each cylinder, an elongated piston rod extending slidably through said cylinders and engaged with said pistons. one end of said rod being adapted to mount a workhead. each piston defining forward and rear chambers in the corresponding cylinder, first fluid passage means communicating with all of the forward chambers, second fluid passage means communicating with at least a major number of the rear chambers, and an elongated tubular body enclosing said cylinders and fluid passage means, each cylinder being defined by a cylindrical wall formed independently of the walls of the adjoining cylinders, said cylindrical walls being releasably engageable with the cylindrical walls of the adjoining cylinder so as to define the series of longitudinally aligned cylinders, at least oneof said cylindrical walls being integrally formed with and interiorly within said tubular body, said tubular body including at least one removable end cap thereon for the introduction of the .rod and cylinders.

21. The tool of claim 20 wherein each of said cylindrical walls other than the cylindrical wall integrally formed with the tubular body is formed independently of said tubular body and generally concentrically positioned with regard thereto in alignment with the integrally formed cylindrical wall. 

1. A force amplifying tool comprising a series of longitudinally aligned cylinders, a piston operatively disposed in each cylinder, an elongated piston rod extending slidably through said cylinders and engaged with said pistons, one end of said rod being adapted to mount a workhead, each pIston defining forward and rear chambers in the corresponding cylinder, first fluid passage means communicating with all of the forward chambers, second fluid passage means communicating with at least a major number of the rear chambers, and an elongated tubular body enclosing said cylinders and fluid passage means, one of said fluid passage means being defined longitudinally through said piston rod, said rod having laterally directed holes therein communicating the interior fluid passage means with the corresponding chambers, the other of said fluid passage means being defined about said cylinders between the cylinders and the tubular body, and fluid passing holes communicating said other fluid passage means with the corresponding chambers, said elongated piston rod being formed of a plurality of releasably interconnected hollow rod sections, at least the majority of said pistons being mounted between adjacent rod sections, each cylinder being defined by an independent cylindrical wall releasably engageable with the cylindrical walls of the adjoining cylinders so as to define the series of longitudinally aligned cylinders, said tubular body including at least one removable end cap thereon for the introduction of the sectionally constructed rod and cylinders.
 2. The tool of claim 1 wherein each of said rear chambers not communicated with the second fluid passage means is substantially airtight upon forward movement of the piston therein whereby a vacuumlike condition is developed which provides an inherent retracting force on the piston and hence the piston rod.
 3. The tool of claim 2 including a one-way check valve in each of said rear chambers not communicated with the second fluid passage means providing for an exhausting of air in the corresponding rear chamber upon a rearward movement of the corresponding piston.
 4. The tool of claim 3 wherein one of said cylinders is integrally formed with and interiorly within said tubular body.
 5. The tool of claim 4 wherein the fluid passage means through the piston rod comprises the first fluid passage means, and the fluid passage means about the cylinders comprises the second fluid passage means.
 6. A force amplifying tool comprising a series of longitudinally aligned cylinders, a piston operatively disposed in each cylinder, an elongated piston rod extending slidably through said cylinders and engaged with said pistons, one end of said rod being adapted to mount a workhead, each piston defining forward and rear chambers in the corresponding cylinder, first fluid passage means communicating with all of the forward chambers, second fluid passage means communicating with at least a major number of the rear chambers, and an elongated tubular body enclosing said cylinders and fluid passage means, said elongated piston rod being formed of a plurality of releasably interconnected hollow rod sections, at least the majority of said pistons being mounted between adjacent rod sections, each cylinder being defined by an independent cylindrical wall releasably engageable with the cylindrical walls of the adjoining cylinders so as to define the series of longitudinally aligned cylinders, said tubular body including at least one removable end cap thereon for the introduction of the sectionally constructed rod and cylinders.
 7. A force amplifying tool comprising a series of longitudinally aligned cylinders, a piston operatively disposed in each cylinder, an elongated piston rod extending slidably through said cylinders and engaged with said pistons, one end of said rod being adapted to mount a workhead, each piston defining forward and rear chambers in the corresponding cylinder, first fluid passage means communicating with all of the forward chambers, second fluid passage means communicating with at least a major number of the rear chambers, and an elongated tubular body enclosing said cylinders and fluid passage means, each of said rear chambers not communicated with the second fluid passage means being substantially airtight upon forward movement of the piston therein whereby a vacuumlike condition is developed which provides an inherent retracting force on the piston and hence the piston rod.
 8. The tool of claim 1 wherein the fluid passage means through the piston rod comprises the second fluid passage means, and the fluid passage means about the cylinders comprises the first fluid passage means.
 9. The tool of claim 8 wherein each of said pistons is integrally formed with one of said piston rod sections.
 10. The tool of claim 9 including a one-piece elongated hollow shaft extending through the piston rod sections, said shaft defining an internal airflow passage and having lateral openings therethrough communicating with the interior of said piston rod sections, and means on the opposite ends of said shaft for engagement with the endmost piston rod sections in a section clamping manner.
 11. The tool of claim 10 including an elongated air passage defined through said body parallel to the cylinder receiving interior thereof and communicated with the cylinder receiving interior thereof via lateral openings.
 12. A force amplifying tool comprising a series of longitudinally aligned cylinders, a piston operatively disposed in each cylinder, an elongated piston rod extending through said cylinders and engaged with said pistons, each piston defining a forward and a rearward chamber in the corresponding cylinder, first airflow means communicated with all of the forward chambers, second airflow means communicated with the rear chambers of a major number os said cylinders, check valve means associated with the rear chambers not communicated with the second airflow means for precluding an introduction of air into said chambers upon a forward movement of the associated pistons whereby a vacuumlike condition is developed therein, and allowing an exhaust of these rear chambers upon a rearward movement of the pistons therein, the pistons in the cylinders having the noncommunicating rear chambers being fixed to the piston rod for forward movement therewith induced by the introduction of pressure through the airflow means communicating with the rear chambers of those cylinders wherein the rear chambers communicate with the second airflow means.
 13. The tool of claim 12 wherein said first airflow means is defined longitudinally through said piston rod.
 14. The tool of claim 12 wherein said second airflow means is defined substantially circumferentially about the cylinders having the communicated rear chambers.
 15. The tool of claim 12 including a pair of cooperating valve units for controlling the flow of air through the first and second airflow means, each valve unit including a pair of spaced valves and spaced valve seats orientated relative to the valves so as to provide for a seating of only one valve at a time, and spring means biasing each valve unit to a predetermined position.
 16. The tool of claim 7 including a one-way check valve in each of said rear chambers not communicated with the second fluid passage means providing for an exhausting of air in the corresponding rear chamber upon a rearward movement of the corresponding piston.
 17. The tool of claim 7 wherein one of said cylinders is integrally formed with and interiorly within said tubular body, the remainder of said cylinders being independent of said tubular body and positioned generally concentrically therewith.
 18. A force amplifying tool comprising a series of longitudinally aligned cylinders, a piston operatively disposed in each cylinder, an elongated piston rod extending slidably through said cylinders and engaged with said pistons, one end of said rod being adapted to mount a workhead, each piston defining forward and rear chambers in the corresponding cylinder, first fluid passage means communicating with all of the forward chambers, second fluid passage means communicating with at least a major number of the rear chambers, each of said rear chambers not communicated with the second fluid passage Means being substantially airtight upon forward movement of the piston therein whereby a vacuumlike condition is developed which provides an inherent retracting force on the piston and hence the piston rod.
 19. The tool of claim 18 including a one-way check valve in each of said rear chambers not communicated with the second fluid passage means providing for an exhausting of air in the corresponding rear chamber upon a rearward movement of the corresponding piston.
 20. A force amplifying tool comprising a series of longitudinally aligned cylinders, a piston operatively disposed in each cylinder, an elongated piston rod extending slidably through said cylinders and engaged with said pistons, one end of said rod being adapted to mount a workhead, each piston defining forward and rear chambers in the corresponding cylinder, first fluid passage means communicating with all of the forward chambers, second fluid passage means communicating with at least a major number of the rear chambers, and an elongated tubular body enclosing said cylinders and fluid passage means, each cylinder being defined by a cylindrical wall formed independently of the walls of the adjoining cylinders, said cylindrical walls being releasably engageable with the cylindrical walls of the adjoining cylinder so as to define the series of longitudinally aligned cylinders, at least one of said cylindrical walls being integrally formed with and interiorly within said tubular body, said tubular body including at least one removable end cap thereon for the introduction of the rod and cylinders.
 21. The tool of claim 20 wherein each of said cylindrical walls other than the cylindrical wall integrally formed with the tubular body is formed independently of said tubular body and generally concentrically positioned with regard thereto in alignment with the integrally formed cylindrical wall. 